Try updating npm by running npm install npm@latest -g. I ran that command and it updated to v4.0.2. The recent updates could contain a fix if it is code related. Command in footer of the npm docs page.

Disabling symlinks helped a number of users when using npm install on systems unable to create symlinks.
To turn off npm using symlinks set bin-links to false in the npm config by running npm config set bin-links false. Optionally you can run npm install --no-bin-links each time. The first command makes the change to the npm config so you don't have to add the --no-bin-links flag each time you run npm install. This is the method recommended in the npm config docs to get npm working on systems/drives that don't support symlinks.